In a power window that raises and lowers a window glass of a vehicle by drive force of a raising/lowering motor, when the window glass is gradually closed by continuously setting an operational switch to be on in a closing direction, a foreign substance may be pinched between the window glass and a window frame.
Thus, a safety device is proposed, in which a detection device is provided for detecting a fact that the foreign substance is pinched between the window glass and the window frame, and when the device detects pinching, it reversely drives a motor to lower the window glass irrespectively of a state of the operational switch (for example, refer to patent document 1). As one pinching detection device in the safety device, a device is known, in which repetitive pulses are generated in accordance with rotational frequency (angle) of the raising/lowering motor, and increase in width of each of the pulses is detected, thereby occurrence of pinching is determined. That is, pulse width in a normal condition is previously stored, and when a value of pulse width during operation is increased to an allowable value or more, the detection device determines that pinching of the foreign substance occurs.
Furthermore, an invention is proposed, in which half pulse width from a rising edge to a trailing edge of a pulse outputted from an encoder and half pulse width from a trailing edge to a rising edge of the pulse are measured to improve accuracy of pinching detection.
Since the raising/lowering motor is driven by a battery mounted in a vehicle, rotational frequency (rotational speed) of the motor is inevitably varied due to variation in voltage of the battery. When rotational speed is varied, pulse width is also varied in accordance with variation of the rotational speed. Therefore, when accurate pinching detection is tried to be performed, possibility of false detection is increased. That is, possibility of false operation is increased: while increase in pulse width is actually due to reduction in source voltage of the battery, the increase may be falsely determined to be caused by pinching of a foreign substance at relatively high possibility. This is completely the same in the case that a source voltage is increased above a reference voltage due to some reason.
Raising speed of the window glass is not constant due to change in sliding resistance or the like even after a certain period has passed from start, and may be changed due to aged deterioration or the like. Therefore, an error is large in a detection method based on detection of increase in pulse width, consequently pinching may be falsely detected at a higher possibility although pinching does not actually occur. Furthermore, in the encoder, a rotational angle during a high level from a rising edge to a trailing edge of a pulse may not be equal to a rotational angle during a low level from a trailing edge to a rising edge of the pulse. When the encoder itself includes an error in this way, a further large error occurs in the method based on detection of half pulse width, leading to increase in possibility of false pinching detection in spite of a fact that pinching does not actually occur.
As a usual example of the encoder, an encoder has been given, in which a cylindrical rotor including a magnet having a plurality of magnet poles is concentrically fixed on a rotating shaft of a raising/lowering motor for raising and lowering a window glass (for example, refer to patent document 2).
In this device, a plurality of N poles and S poles are disposed in a circumferential direction of the rotating shaft of the motor, and a magnetosensitive element disposed near the rotor is used to detect a rotational angle and a rotational direction of the motor rotating shaft, and such detection data are used to detect pinching.
In the device, a larger number of magnetic poles have been necessary to be provided to improve accuracy of pinching detection. However, a magnet having a plurality of magnetic poles is a member high in unit price, causing increase in cost of the device. Moreover, the device has a problem that much time is taken to provide the plurality of magnetic poles, leading to reduction in productivity of the device.
As an approach of controlling a power window, a method is given, in which an automatic mode where a window glass is reciprocated with operation of a user as a trigger between a closing position and an opening position of a window frame while avoiding pinching of a foreign substance, and a manual mode where the window glass is reciprocated according to operation of the user between the closing position and the opening position of the window frame are provided, and when false pinching avoidance is repeated in the automatic mode, the automatic mode is prohibited and only the manual mode is valid (for example, refer to patent document 3).
In such a case, to respond to temporal change in load condition of a motor, learning is conducted on a load condition of the motor in the case that pinching does not occur, and determination of pinching is made based on contents of the learning (for example, refer to patent document 4).
When the automatic mode is stopped due to repeated, false pinching avoidance, a user needs to perform opening and closing of the window in the manual mode. Moreover, even if an automatic mode recovery procedure is described in a manual, the user often does not see the manual, or even if the user sees the manual, it may not necessarily act just according to an instruction of the manual.
When the automatic mode is stopped due to repeated, false pinching avoidance, the user needs to perform full closing of the window in the manual mode. However, since pinching avoidance is not performed in the manual mode, for example, when a power window for a rear seat is closed by operation from a driver seat side, careless pinching of a human body may occur. When pinching avoidance is allowed even in the manual mode in order to avoid this, the window cannot be fully closed when false pinching avoidance is performed.
When a window glass during lowering is reversely raised, a load of a motor is changed in a manner that it is temporarily unloaded and then suddenly increased in the initial stage of raising due to backlash or play of a gear series or wire system. For the initial stage, a threshold value for pinching detection is previously set large compared with a typical threshold value so that such sudden load increase is not misrecognized as pinching of a foreign substance (for example, refer to patent document 5).
In this method, pinching detection sensitivity is bad in the initial stage of the reverse raising of the window glass, since the threshold value is large. Therefore, the pinching avoidance is substantially invalidated, and when pinching actually occurs, large force is applied to an object. In addition, since a period in which the large threshold value is used is set comparatively long in consideration of individual difference of the power window or the like, the large force is applied to the pinched object for a further long time.
When a door is closed during raising the window glass, false reverse-movement of the window glass may occur due to variation in load caused by shock or vibration associated with the door closing. To avoid this, the threshold value is temporarily increased, or a pinching prevention function is temporarily invalidated during door closing. While opening or closing of the door is determined based on an on or off state of a courtesy switch or the like, when a system recognizes the door closing after occurrence of the load variation due to delay in detection of the state of the courtesy switch or delay in transmission of a detection signal or the like, the false reverse-movement of the window glass cannot be prevented (for example, refer to patent documents 6 and 7).
Patent document 1: JP-A-2002-46468
Patent document 2: JP-A-2003-336444
Patent document 3: JP-A-7-317430
Patent document 4: JP-A-10-331524
Patent document 5: JP-A-7-113375
Patent document 6: JP-A-9-32414
Patent document 7: JP-A-9-328964